The present invention relates to an image sensor device. For example, the present invention relates to an image sensor device that generates output image information with a dynamic range higher than a dynamic range which can be achieved by electric charges that can be accumulated during a one-time exposure by a photodiode that outputs image information in the image sensor device.
In recent years, in image sensor devices, a wide dynamic range of output image information is required. In this regard, examples of techniques for expanding a dynamic range are disclosed in Japanese Patent Nos. 4502278 and 4931233.
A solid-state imaging device disclosed in Japanese Patent No. 4502278 includes a photodiode that receives light and generates and accumulates photoelectric charges; a transfer transistor that transfers the photoelectric charges; a floating region to which the photoelectric charges are transferred via the transfer transistor; a storage capacitor element; and a storage transistor provided between the floating region and the storage capacitor element. In the solid-state imaging device disclosed in Japanese Patent No. 4502278, the storage transistor is turned on during an accumulation period of the photodiode, and allows the photoelectric charges, which overflow from the photodiode and flow to the floating region from the transfer transistor, to be accumulated in the storage capacitor element during the accumulation period. Further, during a transfer period subsequent to the accumulation period of the photodiode, the storage transistor is turned off. The transfer transistor is turned on during the transfer period, and allows the electric charges accumulated in the photodiode to be transferred to the floating region and accumulated in the floating region. During a period subsequent to the transfer period, the storage transistor is turned on and allows the electric charges, which are accumulated in the storage capacitor element and overflow, to be mixed with the electric charges accumulated in the floating region. Further, the storage transistor reads out the electric charges accumulated in the floating region before mixing, and also reads out the mixed electric charges after mixing.
An imaging apparatus disclosed in the specification of Japanese Patent No. 4931233 includes: a photoelectric conversion unit that generates electric charges by a photoelectric conversion and accumulates the generated electric charges; an electric charge accumulation unit that accumulates the electric charges overflowing from the photoelectric conversion unit; a read-out unit that reads out, a plurality of times, a signal based on the electric charges accumulated in the electric charge accumulation unit during a single electric charge accumulation period for the electric charges generated by the photoelectric conversion unit; and a reset switch that resets the electric charges accumulated in the charge accumulation unit after each reading by the read-out unit.